The present invention relates to a radial blowing device for a harvester thresher cleaning arrangement which is composed substantially of an upper sieve, a lower sieve and a guiding bottom. More particularly, it relates to a radial blowing device which has at least two blowers with wind passages, wherein each blower has as a double impeller including two sets of blades.
Radial blowing devices for cleaning arrangements of the above mentioned general type are known in the art. The German Pat. No. 289,559 describes a blowing device for a cleaning arrangement of a thresher, wherein baffles are arranged in an outlet passage to provide for uniform distribution of the air volume over the width of the outlet passage. This distribution is attained, as a rule, by such an arrangement of baffles that they can be adjusted relative to one another. The German Pat. No. 289,559 is based on the realization of the fact that especially in wide threshers when the ventilator housing is correspondingly wide, the distribution of the air volume aspirated through the lateral openings into the outlet passage, is not uniform, the air volume considerably decreases from the lateral walls of the passage toward the central region of the same, and thereby the material traveling on the sieve surfaces is not completely cleaned by the air stream in the central region of the sieve.
When one closely examines the operation of the blowing device disclosed in this patent which intends to eliminate the above-mentioned disadvantages, he will come to the conclusion that a uniform action upon the cleaning sieve over its entire working width in the construction with the openable baffles cannot be attained, inasmuch as the known blowing device has an impeller with blades which extend over the entire width of the blower. Subdivision of the blowing device into several partial blowers is not provided, which means that the air volume and air speed decrease toward the central region of the blowing device, they reach the zero value, whereas the baffles alone cannot provide for uniform distribution of the cleaning air.
A blowing device for a grain cleaning arrangement is further known, for example from the U.S. Pat. Nos. 236,340, 2,849,118 and 2,954,123, wherein two blowers are provided which have a common wind outlet passage subdivided by a vertical wall. These blowers do not have double impellers with two inflow separated sets of blades, and no wind baffle normal to the bottom of the wind passage is provided in the latter. For these reason, the cleaning air again cannot act upon the cleaning sieve uniformly over its entire working width. Moreover, the air volume and air speed at the side of the partial blowers are considerably greater than in the central region, whereby this known blowing device has the disadvantage it that it does not provide for a complete cleaning action.
Further, a ventilating device for grain cleaning machines is disclosed in the German Pat. No. 37,594 wherein an upper suction-and-pressure blower and a lower suction blower are provided, which are subdivided into two blowers located at a distance adjacent to one another and supported by a common shaft. The upper suction-and-pressure blower aspirates from a third cleaning arrangement still existing impurities of the machine and acts by the generated pressure air upon the uncleaned grain which travels through a sieve arranged under the vibrator, onto a return bottom. The grain which is cleaned by the upper blower runs through the double suction blower arranged below, so as to be freed from lighter admixtures. This arrangement ensures that with the utilization of two ventilator-units at three locations, cleaning of the grain is attained. However, in this known construction a subdivision of the blowers located at a distance adjacent to one another is not provided and a wind baffle is not arranged. Thereby uniform distribution of the cleaning air over the entire cross section of the outlet of the blowing device is also not guaranteed.
Finally, it is known from the German Auslegeschrift No. 1,403,495 that the radial blowing device is subdivided into at least three blowers with wind passages which aspirate air at both sides, and the air travels through the wind passage via a common outlet opening. Each blower has a double impeller with two inflow separated sets of blades, wherein at least two wind baffles are arranged in the wind passage of each blower normal to the bottom. This arrangement also does not provide for uniform air distribution over the entire region of the cleaning arrangement, inasmuch as one of the wind baffles is arranged at a relatively great distance from the double impeller and thereby turbulence takes place between the double impeller and the wind baffles. On the other hand, this is because the air stream generated from the separate blowers is no longer guided after it leaves the wind passages.